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    Functional Dependencies, Keys and Normalization Short Notes for GATE CS

    Functional Dependencies, Keys and Normalization short notes for GATE CS: 3 study cards covering concepts, formulas, shortcuts and exam traps, plus solved prac

    functional dependencies keys and normalization short notes

    Armstrong's Axioms and FD Inference: Quick Reference

    Quick Reference

    Core Axioms: Reflexivity, Augmentation, Transitivity
    Derived Rules: Union, Decomposition, Pseudotransitivity
    Inference test:
    Trivial FD: (always true)
    Useful FD:
    Common traps: FDs are not symmetric. Cannot shrink left side. Cannot expand right side alone.

    Keys and Closures: Final Revision Checklist

    Final Revision Checklist
    Core Definitions
    • Superkey:
    • Candidate Key: Minimal superkey
    • Prime Attribute: Part of candidate key
    Finding Candidate Keys (L-R-LR-N)
    • L & N: Must be in every candidate key
    • R: Never in any candidate key
    • LR: Test combinations to achieve full closure
    Counting Superkeys
    1 CK:
    Multiple CKs: Inclusion-Exclusion
    Exam Traps
    • Do not confuse superkeys with candidate keys (minimality matters).
    • Always subtract intersections for multiple CKs.
    • Attributes in 'N' are mandatory in every CK.

    Normal Forms and Decomposition: Final Checklist

    Final Revision Checklist
    Normal Forms
    • 1NF: Atomic values.
    • 2NF: No partial dependency (Non-prime Part of Key).
    • 3NF: No transitive dependency (Non-prime Non-prime). Rule: iff is Superkey OR is Prime.
    • BCNF: Strict. Rule: iff is Superkey.
    Decomposition Properties
    • Lossless Join: is superkey of or .
    • Dependency Preserving: Every FD in is contained in some .
    Golden Rule:
    3NF: Always Lossless + Dependency Preserving.
    BCNF: Always Lossless, but MAY NOT be Dependency Preserving.
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    Functional Dependencies, Keys and Normalization Short Notes for GATE CS

    Functional Dependencies, Keys and Normalization short notes for GATE CS: 3 study cards covering concepts, formulas, shortcuts and exam traps, plus solved practice questions.

    Armstrong's Axioms and FD Inference: Quick Reference

    Quick Reference

    Core Axioms: Reflexivity, Augmentation, Transitivity
    Derived Rules: Union, Decomposition, Pseudotransitivity
    Inference test:
    Trivial FD: (always true)
    Useful FD:
    Common traps: FDs are not symmetric. Cannot shrink left side. Cannot expand right side alone.

    Keys and Closures: Final Revision Checklist

    Final Revision Checklist
    Core Definitions
    • Superkey:
    • Candidate Key: Minimal superkey
    • Prime Attribute: Part of candidate key
    Finding Candidate Keys (L-R-LR-N)
    • L & N: Must be in every candidate key
    • R: Never in any candidate key
    • LR: Test combinations to achieve full closure
    Counting Superkeys
    1 CK:
    Multiple CKs: Inclusion-Exclusion
    Exam Traps
    • Do not confuse superkeys with candidate keys (minimality matters).
    • Always subtract intersections for multiple CKs.
    • Attributes in 'N' are mandatory in every CK.

    Normal Forms and Decomposition: Final Checklist

    Final Revision Checklist
    Normal Forms
    • 1NF: Atomic values.
    • 2NF: No partial dependency (Non-prime Part of Key).
    • 3NF: No transitive dependency (Non-prime Non-prime). Rule: iff is Superkey OR is Prime.
    • BCNF: Strict. Rule: iff is Superkey.
    Decomposition Properties
    • Lossless Join: is superkey of or .
    • Dependency Preserving: Every FD in is contained in some .
    Golden Rule:
    3NF: Always Lossless + Dependency Preserving.
    BCNF: Always Lossless, but MAY NOT be Dependency Preserving.

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